Diamond SOI (SODOS, silicon-on-diamond-on-silicon), Diamond-on-Silicon, and Thin Silicon-on-Thick Diamond process technologies are being developed to enhance heat flow through a substrate for use in high power devices. In the case of SODOS, the buried diamond layer is used as a heat sink, a heat spreader that reduces the temperature of semiconductor devices operating at high power in the device silicon. Thermal conductivity of diamond is ten times better than silicon and one thousand times better than oxide.
Despite high-purity components used in an HFCVD reactor (Hot Filament Chemical Vapor Deposition), elevated levels of mobile heavy metal ions have been found to out-diffuse from the diamond and seed layer into the adjacent device silicon layer, thus degrading the quality of the silicon and reducing electron and hole current carrier lifetime. During subsequent diffusion operations, these ions can out-diffuse from the diamond and silicon layers and cross-contaminate fabrication processing equipment.
An improved diamond SOI device and method of forming the same would be desirable, in which a barrier can be formed between the diamond SOI layer and the device silicon layer to block diffusion of ions and improve carrier lifetime of the device silicon.
A further modification of the barrier above can be desirable, in which the barrier is a nitride and a back side nitride etch is used followed by a growing a thick oxide on the back side of the device wafer, prior to bonding the device wafer to a handle wafer.
An improved diamond SOI device and method of forming the same would be desirable, in which diamond and nitride layers can be formed on a handle wafer rather than a device wafer, to maintain integrity of the device wafer.
It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the inventive embodiments rather than to maintain strict structural accuracy, detail, and scale.